The four colored Windows logo may not be used as the logo for Windows 8 and it may just be replaced by a new monochrome logo that looks nothing like how we recognize Windows.
Windows Logo Changed: Rumors Suggest new Logo Is Monochrome
Cnbeta.com has put up a new image that shows a new Windows logo and claims that to be the authentic Windows logo that will be used for Windows 8. The logo is completely monochrome and looks nothing like the familiar four color logo that we know now. So if this post is correct then Microsoft has gone the whole hog when recreating Windows and has made a new logo for it too.
However, it is also entirely possible that the logo is correct and the monochrome nature is just for a specific stage like boot up, since complex boot sequences might require resources that Microsoft is not ready to part with.
This logo shows distinct characters of a Metro influenced design. It is very two-dimensional in nature and makes no attempt to flashy. It is definitely flat by design. As with any other major changes to well-established brands, especially the logo itself, there will be a lot of people who will absolutely hate this. But as all things work, this too shall pass and people will just get used to it. Now the real debate is whether this is true at all.
The consumer preview for Windows 8 is coming out at the end of this month, in fact on the very last day itself. If Microsoft has really changed the logo then it should reflect in this build because it is meant to give regular users a fully loaded version of Windows 8 that is feature-complete and just a little rough around the edges.